Leading article: Nothing less than the future of Afghanistan is at stake

Operation Moshtarak, which has been mounted to recapture a key area of Afghanistan's Helmand Province from the Taliban, has now begun in earnest. British troops are reported to have moved in on the northern district of Nad Ali and the Americans to have begun their advance on Marjah to the south. They have been joined by other members of the international coalition, and – for the first time in such a large enterprise – by members of the growing Afghan army. An enormous amount is at stake, and not only on the ground.

The heavy advance publicity for this operation was clearly designed to send messages to a variety of audiences. It was intended to convince an increasingly doubtful public in the United States and Britain that the allied presence in Afghanistan has a defined purpose that can be met. It was designed to communicate the same thing to Afghans, in Helmand Province and beyond, but also to persuade them that Nato forces are capable not just of winning, but of holding territory, and then handing it over to Afghans themselves to run and police.

And, of course, it was designed to give the Taliban and the local civilian population ample warning of the likely hostilities to come. They would thus have a chance to leave or to abandon the insurgency and change sides.

Trying to communicate at once with so many different audiences, however, holds risks and the risk is particularly evident in relation to the Taliban. On the one hand, Nato has embarked on what is being presented as a major offensive against Taliban-controlled areas. On the other, it is stressing, with the government of the President Hamid Karzai, that it wants to court so-called "moderate" Taliban with a view to their reintegration into the mainstream. The two messages can just about be reconciled, but that may not be so evident on the ground.

Which is where, in the end, Operation Moshtarak will be won or lost. The first signs are that many Taliban fighters have melted away, just as they did in 2001, when the Western intervention first began. If this is so – and it is very early days to make such a judgement – the bulk of the Taliban forces will only have been displaced rather than defeated. Taking control of this particular territory, however significant it is strategically, might then not be enough.

In the best case, Nato and Afghan forces will show that they can operate together; the land recaptured will be adequately secured, and the promised reconstruction will show swift results. The local population will see the benefits both of security and of a local government not beholden to the Taliban. Both Nato and President Karzai would then be able to hold up this part of Helmand Province as proof that peace and security can be restored, not just here, but in the province and the country as a whole. Success could turn the tide of the war and make possible the progressive withdrawal of foreign troops.

This is the thinking behind the tactics recommended by the US commander, General Stanley McChrystal, and approved by President Obama. If either the territory or the trust of the local population cannot be won back, however, prospects for a foreseeable end to the Nato mission look much less rosy. There is much – from fiercer than anticipated Taliban resistance to a large number of civilian casualties – that could go wrong. It will be weeks, not days, before the results of Operation Moshtarak are apparent; reports of early or easy success, from either side, should be treated with utmost caution.